Re: Guys say 656 has bad Ballast Resistor.. but w

Posted by John T on July 06, 2006 at 07:16:47 from (66.244.90.5):

In Reply to: Guys say 656 has bad Ballast Resistor.. but where posted by R. Smith on July 05, 2006 at 22:33:46:

To begin with Ive never owned a 656 but have been around the electrical block quite a few times and a state fair n a goat roping or two so may still be able to shed some light on your question.......... (Dont ya just love disclaimers lol, I became an attorney after retiring from EE and cant help myself, sorry)

Iffffffffff it really has an external voltage dropping (12 to 6) Ballast Resistor it would be located in series AFTER the IGN output on an Ignition Switch and BEFORE the coils high input (NOT to distributor) lil terminal. Typical ones are maybe 1/2 inch square by maybe 3 inches long white bathtub shaped.

HOWEVERRRRRRRRRRR some tractors may have made use of a resistive wire link (looks about like regular wire) or even a link of heat compensatng wire which functions as a Thermistor, but those didnt require any start up ballast by pass circuit, I JUST CANT SAY FOR SURE sitting here what, if anything, you may or may not have. Also Im not sure if they used resistive wire in such a high power (maybe 25 watts) application, could have I guess.

ALSO if the coil were a true full 12 volt rated (some call internally ballasted) coil on a 12 volt tractor, there shouldnt be any sort of ballast resistor or resitive wire or thermistor in the first place.

On those tractors that have BOTH an external ballast resistor PLUS a working start ballast by pass system (mechanical or an extra lil I terminal on a solenolid or in the switch set up) they are the ones where IF THE BALLAST IS BAD/OPEN they will run (coil has voltage) while being cranked but NOT otherwise.

Sooooooooo if it has an external ballast resistor or a link or resistive wire (same as a ballast) this may help you find it!!!!!!!!! and remember, if it has such it would need some sort of start up ballast by pass circuit for it to apply full unballasted battery voltage to a 6 volt coil ONLY while cranking, but then switch back to the 6 volt ballasted coil voltage while running.

I would place a voltmeter on the coils high input (NOT to distributor) terminal and measure what the voltage is when shes cranking and then when the switch is still ON while NOT cranking, that will tell the story. When you just turn the ignition switch to ON (if points closed and all is working) the coils input voltage should be around 6 volts (if it has a good n working series ballast) but then when the engine is being cranked it should rise to battery voltage which is some less then 12 depending on battery n temperature n starter shape etc. In the event when you turn the Ignition ON theres no voltage getting to the coil at all but there is voltage while cranking, thats the CLASSICAL signs of an open bad external ballast resistor

ORRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR it could be a bad Ignition Switch !!!!!!!!!!!!!!! If the ignition switch were bad it could be failing to provide battery voltage on its IGN output terminal when switched to ON butttttttttt the ballast by pass circuitry could still provide coil voltage while cranking

YOU BETTER PUT A VOLTMETER OR TEST LAMP ON THE IGNITION SWITCHES IGN OUTPUT (to ballast or coil) TERMINAL TO VERIFY ITS HOT WHEN SWITCHED TO ON

If not try to hot wire voltage ahead of the ballast (if it has one) n see if she runs then????????? and if so its an ignition switch problem instead of a bad/open ballast.

If theres noooooo voltage on the coils input when the switch is ON,,,,,,,,its either a bad/open ballast (if it has one) or a bad switch or bad wiring from switch to coil

CLEAR AS MUD????????/

Best wishes n God Bless

John T

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